With the digital switching amplifiers, neodymium woofers and well designed structure, it is one of the smallest and lightest double 18in systems available. A unique feature is the semi charged horn design which at low frequencies around 40 Hz operates as a conventional bass reflex cabinet. However at slightly higher frequencies in the 80 to 100 Hz area, the system operates as a semi charged horn loaded design which provides around 3 to 4 dB more efficiency.